Explained: Transiting exoplanets
In the quest to find life elsewhere in the universe, planetary scientists have detected more than 500 planets outside the solar system, or exoplanets, over the past 15 years. About one-fifth of those were discovered by scanning the sky for any change in a star’s brightness that might be caused by a planet passing in front of that star as seen from Earth. Known as a transit, this event is essentially an eclipse, but instead of blocking an entire celestial body from view, as the Moon does to the sun during a solar eclipse, a transiting planet obscures just a tiny fraction of the light from its parent star. Astronomers use ground-based telescopes to detect these tiny fractions — changes as small as 0.25 percent. Then they try to confirm a planet’s existence through careful follow-up observations.The discovery of the first transiting exoplanet in 1999 provided a way to study...